The present invention pertains generally to inorganic polymer synthesis and in particular to highly thermally stable silicon containing thermoplastic polymers.
A number of modified siloxane polymers have been prepared. Although polymers based on poly(dimethyl siloxane) offer uncommonly good thermal stability, the polymer backbone tends to form a helical structure which aids in the formation of cyclic siloxanes at elevated temperatures. In order to prevent cyclic formation, siloxane copolymers with modified backbones are synthesized by the addition of organic and inorganic groups. These groups inhibit the reversion to cyclics through steric and/or electronic effects, and improve the thermal stability. Examples of such copolymers are arylene-siloxane copolymers, e.g., (--OSi(CH.sub.3).sub.2 C.sub.6 H.sub.4 Si(CH.sub.3).sub.2 SiR.sub.2 --).sub.x and carborane-siloxane copolymers.
Phthalocyanines display several useful properties which would make their incorporation into siloxane polymers valuable in addition to preventing cyclic formation. In general, phthalocyanine compounds are noted for their intense colors and high thermal stabilities. It is expected that siloxane polymers containing a phthalocyanine nucleus would be useful as dyes, coatings, and toughening agents for highly thermally stable resins such as polyimides and poly(phthalocyanines). Unfortunately, the known siloxane-phthalocyanine copolymers are insoluble, nonmeltable, and noncrosslinkable. Their insolubility seriously limits workability and their usefulness as coatings. Their nonmeltability and noncrosslinkability prevents their use as strengthening agents. Consequently, these compounds have been little more than laboratory curiosities.